"Even as climate change shrinks some populations of arctic animals like polar bears and caribou, beavers may be taking advantage of warming temperatures to expand their range. But as the beavers head north, their very presence may worsen the effects of climate change.

The issue isn’t just that the beavers are moving into a new environment — it’s that they’re gentrifying it.

Take the dams they build on rivers and streams to slow the flow of water and create the pools in which they construct their dens. In other habitats, where the dams help filter pollutants from water and mitigate the effects of droughts and floods, they are generally seen as a net benefit. But in the tundra, the vast treeless region in the Far North, beaver behavior creates new water channels that can thaw the permanently frozen ground, or permafrost."

Kendra Pierre-Louis reports for the New York Times December 20, 2017. [2]